The present invention relates to a light radiator capable of effectively and diffusedly radiating into water or other dirty places the light transmitted through a fiber optic cable or the like, in particular, a light radiator to be preferably used as a source of light energy for the photosynthetic process used in producing chlorella and other like organic substances.
In recent years, in relation to the necessity for saving energy, the effective utilization of solar energy has been actively studied and developed in various fields. The most effective utilization of solar energy is as light energy without its further being converted into thermal or electrical energy. With this in mind, the present applicant has proposed various methods and systems for channeling solar rays focused by means of a lens system, or the like, into a fiber optic cable and to transmit the same therethrough to wherever the light is needed for illumination or other purposes, as for example, for promoting the cultivation of plants, for the propagation of chlorella, for feeding fishes, for giving beauty treatments through sunbathing, for giving medical treatments through light radiation etc. If light rays are emitted from the cut end of a fiber optic cable, they can be radiated only within a small radiation angle of about 46.degree. since focused light rays have a certain directivity. Therefore, the desired light radiation for the above-mentioned purposes may not be obtained if light is directly emitted from the cut end of the fiber optic cable. In order to solve this problem, the present applicant has also proposed various kinds of light radiators which can effectively diffuse the light rays transmitted through a fiber optic cable and to radiate the same to any desired place.
On fish farms, feeding small fish requires a great amount of zoo-plankton which eats chlorella to propagate itself. To effectively propagate chlorella it is necessary to properly supply the chlorella with sunlight and carbon dioxide. Generally, when chlorella increases, the light is obstructed and cannot reach the chlorella that is in the deeper areas, that is, the light which is obstructed cannot be distributed evenly to all of the chlorella plants. In view of this problem, in the past, the present applicant has proposed various chlorella cultivating apparatus which are capable of equally providing light energy to all of the chlorella in a cultivating tank by using a large number of 'pointed' light ray sources properly arranged therein.
A light radiator previously proposed by the present applicant comprises a light guide and a groove spirally cut on the surface of said light guide.
The light, introduced into the light guide, is reflected on a grooved portion thereof and effectively radiated therefrom for use as illumination and for other intended purposes as mentioned above.
In this case a substantially uniform radiation of the light from the whole body of the light guide may be realized if the spiral groove is made in such a way that the spiral pitch gradually becomes narrow or the groove itself gradually deepens in the direction of the light. Furthermore, when a reflecting plate or the like is placed at the end-face of the light guide, the light reflected by the reflecting plate enters into the light guide and then is radiated therefrom.
The light guide may be hermetically enclosed in a semi-transparent or transparent container to protect the light guide from being damaged by striking and also to eliminate the possibility of injury to a person's hand by the edge of its slotted or concave portion. Furthermore, when the light guide, thus protected in a container, is used in water as a light source for cultivating chlorella, or for feeding fishes it can be protected from a kind of fur forming on its surface.
Since the light guide is surrounded by an air layer in the container, the light can be radiated therethrough at a desirable angle and/or can be scattered as needed.
If the light guide, without the protective container, is used in water, its slotted or concave portion is filled with water, resulting in the light being radiated only from the limited end-surface of the light guide since the light reflection coefficiency scarcely changes at the slotted or concave portion.
In the above-mentioned light radiator there is a gap between the light guide and the container. In the case of placing a large number of said light radiators in a tank filled with a solution for cultivating chlorella, the density of the light guides can be reduced in relation to the total of the above-mentioned gaps.